Beyond this its junction with the fifth, it is no longer possible to trace any special nerve, or to indicate its subdivisions by names, since, on the masseter, a succession of diverging branches are given off from it, each of which, by uniting with its neighbours above and below, and giving off fresh ramifications from the branches of union, forms part of a com plicated network, in which the original con stituent branches, and the respective shares which they take in the new loops, can scarcely be recognized. Cruveilhier and Bonamy have traced this looped arrangement still more minutely, having followed it into the smallest branches of the nerve, and especially into those which supply the orbicularis ; and it has been likened by them to the mode in which the mesenteric arteries break up to reach the intestine.
Notwithstanding this free communication, however, the different portions of this re ticulated arrangement may be conveniently regarded in succession, in order the better to appreciate their distribution.
Superiorly are the temporal branches ; these emerge from beneath the upper border of the parotid, and cross the zygoma to be distri buted to the superficial muscles of the auricle, the attollens and attrahens aurem, and to the anterior belly of the occipito-frontalis beyond these. The orbital branch of the second division of the fifth joins, by its long ascending filaments, with these branches of the facial; so also a perforating filament from the deep temporal of the third division, with others from the auriculo-temporal of the same portion of the fifth, are usually traceable to an union with this nerve.
Anteriorly to these are the numerous or bicular or supra-orbital branches. They pass obliquely forwards and upwards over the malar bone, to supply the orbicularis palpe brarum, and corrugator snpercilii muscles. Their connection with the fifth occurs chiefly by the supra-orbital and lachrymal of the oph thalmic division ; but others join the malar branch of the second division, where it emerges from its foramen in the malar bone near the outer angle of the orbit.
The infra-orbital filaments pass almost hori zontally forwards from the temporo-facial divi sion towards the side of the nose. In this course, accompanied by the parotid duct, they cross over the masseter muscle; and more anteriorly, they pass beneath the different muscles which descend to the angle of the mouth and upper lip, anti are distributed to them by numerous filaments which enter their deep surface. In this manner the greater and lesser zygomatic, with the proper and common elevator of the lip, and the elevator of the angle of the mouth, receive their ner vous supply ; and the pyramidalis and trans versalis nasi also obtain filaments from this part of the facial. Many of these, in passing
forwards, unite at right angles with the ra diating bundles of filaments into which the infra-orbital nerve divides after leaving the foramen of the same name. Besides this Union with the second division of the fifth, it unites with the ophthalmic by a small twig of its nasal branch, which appears between the lateral cartilage and the nasal bone, and generally by an infra-trochlear filament of the same portion in the angle of the eye.
The buccal branches, with the same direction as the preceding, occupy a position at a some, what lower level on the face, in the neigh bourhood of the transversalis faciei artery. They mostly terminate in the upper half of the orbicularis oris, and in the buccinator, on which muscle they join with the buccal branch of the inferior maxillary division of the fifth. This latter nerve is distributed to the mucous membrane and integuments, and probably has no share in the supply of the muscle. The lower of these buccal branches join another portion of the network, which results from the ramification and union of the next division of the facial.
The cervico-facial division, of smaller size than the temporo-facial, passes downwards and forwards from the seat of bifurcation of the portio dura, and emerges from the parotid gland near the angle of the lower jaw. Here it divides and subdivides in the smile manner as the preceding portion. It is divided into a facial and cervical, or a supra and infra maxillary part.
Its supra-maxillary part is constituted by one or two large branches, which, breaking up as they pass forwards to the interval be tween the jaw and mouth, enter beneath the platysma and triangularis menti ; and besides supplying these and the other muscles of this region, they join with a branch of the inferior dental which comes through the mental fora men.
The infra-maxillary, or cervical portion of the facial nerve, consists of two or three branches, which, directed still more obliquely downwards, soon divide into very numerous filaments. These pass beneath the platysma to gain the upper and anterior part of the neck, where they form looped ramifications, the most inferior of which are traceable in a vertical direction to a short distance below the hyoid bone. They are chiefly distributed to the platysma, and above they join with the neighbouring supra-maxillary branches just mentioned. They unite beneath the platysma with one, or more usually with two, branches from the superficial cervical nerve of the cer vical plexus, which turns round the posterior border of the sterno-mastoid muscle to supply the integuments of the same part of the neck.